The present invention relates to a distortion correction circuit that retrieves data for an image to correct distortion in the image, and relates to, for example, a distortion correction circuit that corrects an image formed by an imaging device with an optical system having a distortion characteristic.
In recent years, digital cameras, with an increasing number of pixels being recordable, are required to include optical systems having higher performance. For a digital camera using a built-in lens, an exclusively designed lens is used. For a digital camera using changeable lenses, various lenses, each having a unique distortion characteristic, are used. A digital camera incorporated in a mobile telephone typically includes an inexpensive optical system. The distortion characteristic of an inexpensive optical system is usually poor. Thus, there is a demand for techniques that correct the distortion characteristic of an optical system to obtain high-quality images.
For a film camera, a lens designed to minimize distortion of an image is typically used. A digital camera processes image data retrieved in an imaging device via an optical system (lens, focusing mechanism, etc.) and corrects the distortion to obtain an image. Japanese Laid-Open Patent Publication No. 11-250239 describes a correction process executed in a digital camera. In the correction process, the addresses of all the pixels of an image prior to distortion correction are calculated using a coefficient of an approximate polynomial representing an image height—distortion curve, which represents the performance characteristic of a lens. Then, the distortion of the image is corrected using the calculated addresses.